The present invention relates generally to bladed rotors for gas turbine or turbojet engines, and more particularly to a new lightweight bladed rotor configuration compatible with continuously-reinforced composite materials.
In conventional gas turbine engines, gases, generally atmospheric air, are compressed in a compressor section and then passed to a combustion section where fuel is added and the mixture burned to add energy to the gases. The now high energy combustion gases are next passed to a turbine section where a portion of the energy is extracted and applied to drive the engine compressor. The remaining still high energy combustion gases are then exhausted from the rear of the engine to provide forward thrust.
Typically, both the compressor and turbine sections include a number of alternate annular rows of fixed stator vanes and movable rotor blades. The stator vanes are generally attached to the inside circumferential wall of the turbine engine and extend radially inward. The rotor blades are generally attached to a rotor and extend radially outward. Each annular row of stator vanes directs the gases to a preferred angle of entry into a downstream annular row of rotor blades.
Modern, and future, high performance turbine engines place very high stresses on the rotors, primarily from centrifugal force. This force is also often termed an outward radial pull. High operating temperatures place an added burden on the ability of rotors and blades to withstand high centrifugal forces due to creep and reduced yield strength.
The traditional configuration for a highly stressed turbine engine rotor made of monolithic material is a disk. The blades are typically attached to the disk around its periphery. The rotor disk generally includes a hole in its center for a shaft.
To provide rotors and blades able to withstand higher stresses, the prior art has experimented with the use of composite materials in a variety of different configurations. A fuller description of those prior art approaches is included as part of the Detailed Description.
Unfortunately, these prior art attempts to utilize composite materials for rotor construction have not been completely successful. For example, the composite disks are difficult to manufacture, especially in larger rotor sizes. Differences in the coefficient of thermal expansion between the fibers and the matrix material can lead to high residual stresses after manufacture. High operating stresses can also result from the combination of thermal expansion, geometric constraints and lack of plasticity of the fibers in the composite. These stresses degrade both material properties and component performance. Layup of fibers can be difficult or tedious. Often, the disk will require a region near its center of thicker cross-section in order to withstand the higher stresses developed in that region. Woven or braided fibers, which can be used in the center region to provide the needed additional strength, can be very difficult to uniformly infiltrate with the matrix material due to the thickness of the cross-section. Finally, adding continuous fiber reinforcement desirably extending from the disk into the blades adds substantially to complexity and difficulty.
Thus it is seen that there is a need for new rotor and blade configurations which successfully take advantage of the physical properties of composite materials.
It is, therefore, a principal object of the present invention to provide a new blade and rotor configuration particularly compatible with continuously-reinforced composite materials.
It is a feature of the present invention that all of its component parts can be advantageously constructed using fiber reinforced composite materials.
It is an advantage of the present invention that its new configuration can be significantly lighter than typical prior art configurations.
It is another advantage of the present invention that it removes the problem of attachments and discontinuities in the highly stressed area of the attachment of blades to rotor disks.
It is a further advantage of the present invention that it will be simple and straightforward to manufacture.
These and other objects, features and advantages of the present invention will become apparent as the description of certain representative embodiments proceeds.